1. Field of the Invention
The invention relates to a process for the preparation of functionalized elastomer/bitumen compositions with a wide plasticity range. It further relates to the application of the compositions obtained to the production of coatings and in particular of road surfacings, of bituminous mixes or else of watertight facings and it also relates to a mother solution which can be employed for the preparation of the said compositions.
2. Background Art
A description is given, in the citation U.S. Pat. No. 4,011,184, of a process for the preparation of functionalized elastomer/bitumen compositions, one of the methods of preparation of which consists in bringing a bitumen into contact, the operation being carried out at temperatures of between 100.degree. C. and 200.degree. C. and with stirring, with an elastomer, particularly a block copolymer of styrene and of a conjugated diene, in an amount representing 0.1% to 25% and very especially 1% to 5% by weight of the bitumen, and an ethylenically unsaturated carboxylic acid or an anhydride of such an acid, for example maleic anhydride, in a proportion corresponding to 0.5% to 10% of the weight of bitumen and of elastomer, the said contact being maintained for a time sufficient to produce, within the bitumen, a functionalized elastomer carrying carboxylic acid or carboxylic acid anhydride functional groups capable of creating directly, by formation of hydrogen bonds, or by addition of a salifying agent capable of reacting with the carboxyl groups, temperature-reversible bridgings between the macromolecular chains of the elastomer and/or between the said macromolecular chains and the bitumen.
The functionalized elastomer/bitumen compositions obtained as indicated above are less susceptible to gelling phenomena than elastomer/bitumen compositions produced by crosslinking elastomers, such as, in particular, block copolymers of styrene and of a conjugated diene, such as butadiene or isoprene, with sulphur within a bitumen. It is possible, for this reason, to produce functionalized elastomer/bitumen compositions which have a high elastomer content and which can act as concentrates. These compositions are more economical to prepare, to store, and to transport than the corresponding compositions with a lower elastomer content and they can be easily diluted at the time of use, by addition of bitumen, in order to form the elastomer/bitumen binders with a lower elastomer content which are commonly used for the preparation of coatings and in particular of road surfacings.
However, the functionalized elastomer/bitumen compositions prepared by using the abovementioned technique described in the citation U.S. Pat. No. 4,011,184 only have to a limited degree carboxyl functional groups attached to the macromolecular chains of the elastomer associated with the bitumen and capable of inducing crosslinkings or bridgings of the said chains with one another and/or with the bitumen, directly or after addition of the salifying agent. For this reason, the physicomechanical characteristics of such compositions, in particular plasticity range (difference between the ball-and-ring softening temperature and the Fraass brittleness point) and mechanical characteristics at low temperatures of use, are not entirely satisfactory.